You turn her off in the settings, which should be enough.
If you want to erase every trace of her, you'll need to use Windows 8.1 or earlier or Linux (if on PC) or Windows Phone 8.0 or earlier or another mobile OS entirely.
There is no reason why you should not be able to delete Cortana. It is purely Microsoft trying to dominate your life and to use your resources on your computer for its own benefit.
There is no reason why you should not be able to delete Cortana. It is purely Microsoft trying to dominate your life and to use your resources on your computer for its own benefit.